Orthopaedic Implant and Fastener Assembly

ABSTRACT

Systems, devices and methods are disclosed for treating fractures. The systems, devices and methods may include one or both of an implant, such as an intramedullary nail, and a fastening assembly, such as a lag screw and compression screw assembly. The implant in some embodiments has a proximal section with a transverse aperture and a cross-section that may be shaped to more accurately conform to the anatomical shape of cortical bone and to provide additional strength and robustness in its lateral portions, preferably without requiring significant additional material. The fastening assembly may be received to slide, in a controlled way, in the transverse aperture of the implant. In some embodiments, the engaging member and the compression device are configured so that the compression device interacts with a portion of the implant and a portion of the engaging member to enable controlled movement between the first and second bone fragments. This configuration is useful for, among other things, compressing a fracture.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/426,088, filed Apr. 17, 2009, is a continuation of U.S. applicationSer. No. 11/963,218, filed Dec. 21, 2007, is a continuation of U.S.application Ser. No. 11/842,979, filed Aug. 22, 2007, and is acontinuation of U.S. application Ser. No. 11/840,381, filed Aug. 17,2007. U.S. application Ser. No. 12/426,088 is a continuation of U.S.application Ser. No. 11/963,218, filed Dec. 21, 2007 and U.S.application Ser. No. 11/840,381, filed Aug. 17, 2007, both of whichclaim priority to U.S. application Ser. No. 10/658,351, filed Sep. 8,2003, now abandoned. U.S. application Ser. No. 11/963,218 is acontinuation of U.S. application Ser. No. 10/936,996, filed Sep. 8,2004, now U.S. Pat. No. 7,527,627, which is a continuation of U.S.application Ser. No. 10/658,351, filed Sep. 8, 2003, now abandoned. U.S.application Ser. No. 11/842,979 is a divisional of U.S. application Ser.No. 10/936,996, filed Sep. 8, 2004, now U.S. Pat. No. 7,527,627, whichis a continuation of U.S. application Ser. No. 10/658,351, filed Sep. 8,2003, now abandoned. U.S. application Ser. No. 11/840,381 is acontinuation of U.S. application Ser. No. 10/937,075, filed on Sep. 8,2004, now U.S. Pat. No. 7,534,244, which is a continuation of U.S.application Ser. No. 10/658,351, filed Sep. 8, 2003, now abandoned. Allof these applications are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to a system for coupling boneportions across a fracture and, more specifically, to an intramedullarynail or plate and screw assembly used to treat fractures of long bonessuch as the femur, humerus and tibia, and various periarticularfractures of these and other bones.

BACKGROUND OF THE INVENTION

There are a variety of devices used to treat fractures of the femur,humerus, tibia, and other long bones. For example, fractures of thefemoral neck, head, and intertrochanteric region have been successfullytreated with a variety of compression screw assemblies, which includegenerally a compression plate having a barrel member, a lag screw and acompressing screw. Examples include the AMBI″ and CLASSIC™ compressionhip screw systems offered by Smith & Nephew, Inc. In such systems, thecompression plate is secured to the exterior of the femur, and thebarrel member is inserted in a predrilled hole in the direction of thefemoral head. The lag screw has a threaded end, or another mechanism forengaging bone, and a smooth portion. The lag screw is inserted throughthe barrel member so that it extends across the break and into thefemoral head. The threaded portion engages the femoral head. Thecompression screw connects the lag screw to the plate. By adjusting thetension of the compression screw, the compression (reduction) of thefracture can be varied. The smooth portion of the lag screw is free toslide through the barrel member to permit the adjustment of thecompression screw. Some assemblies of the prior art use multiple screwsto prevent rotation of the lag screw relative to the compression plateand barrel member and also to prevent rotation of the femoral head onthe lag screw.

Intramedullary nails in combination with lag screws or other screwassemblies have been successfully used to treat fractures of the femur,humerus, tibia, and other long bones as well. A significant applicationof such devices has been the treatment of femoral fractures. One suchnailing system is the IMHS® system offered by Smith & Nephew, Inc., andcovered at least in part by U.S. Pat. No. 5,032,125 and various relatedinternational patents. Other seminal patents in the field include U.S.Pat. Nos. 4,827,917, 5,167,663, 5,312,406, and 5,562,666, which are allassigned to Smith & Nephew, Inc. These patents are all herebyincorporated by reference. A typical prior art intramedullary nail mayhave one or more transverse apertures through its distal end to allowdistal bone screws or pins to be screwed or otherwise inserted throughthe femur at the distal end of the intramedullary nail. This is called“locking” and secures the distal end of the intramedullary nail to thefemur. In addition, a typical intramedullary nail may have one or moreapertures through its proximal end to allow a lag screw assembly to bescrewed or otherwise inserted through the proximal end of theintramedullary nail and into the femur. The lag screw is positionedacross the break in the femur and an end portion of the lag screwengages the femoral head. An intramedullary nail can also be used totreat shaft fractures of the femur or other long bones.

As with compression hip screw systems, intramedullary nail systems aresometimes designed to allow compression screws and/or lag screws toslide through the nail and thus permit contact between or among the bonefragments. Contact resulting from sliding compression facilitates fasterhealing in some circumstances. In some systems, two separate screws (orone screw and a separate pin) are used in order, among other things, toprevent rotation of the femoral head relative to the remainder of thefemur, to prevent penetration of a single screw beyond the femoral head,and to prevent a single screw from tearing through the femoral neck andhead. When an additional screw or pin is used, however, unequal forcesapplied to the separated screws or pins can cause the separate screws orpins to be pressed against the sides of the holes through which theseparate screws or pins are intended to slide. This may result inbinding, which reduces the sliding of the screws or pins through thenail. Conversely, a problem can result from excessive compression of thefemoral head toward or into the fracture site. In extreme cases,excessive sliding compression may cause the femoral head to becompressed all the way into the trochanteric region of the femur.

Furthermore, overly rigid nails sometimes generate periprostheticfractures in regions away from a fracture site. Therefore, it isimportant that intramedullary nails be adequately flexible in comparisonto the bones in which they are implanted. The harder, generally outerportion of a typical bone is referred to as cortical bone. Cortical boneis usually a structurally sound load-bearing material for support of animplant. A cross-section of a long bone that shows the typicalanatomical shape of cortical bone generally reveals a non-circular ringof cortical bone which surrounds a medullary canal. Accordingly, themedullary canal generally features a non-circular cross section.Intramedullary nails of the prior art, however, are usually round orsquare in cross-section, and therefore not anatomically consistent withthe cortical bone or the medullary canal. Some have addressed thisproblem by reaming the medullary canal of the bone with a round reamerin order to cause the nail to fit the cortical bone. This approach,however, can remove significant portions of healthy cortical bone.

The problem of providing an effective load bearing physical relationshipbetween an implant and cortical bone in the proximal femur has beenaddressed in the art of hip replacement devices. Various hip stems havebeen developed which feature generally non-circular cross sections alongtheir length, in order better to fit the anatomically shaped corticalbone of the proximal femur and thus more evenly and effectivelydistribute the load between the stem and the bone. However, none ofthese hip stems have been incorporated into a nail or configured toaccept a screw or screws useful in repairing substantially all of theportions of the treated bone. Instead, hip stems as a general matterhave been considered as a device for replacing portions of a long bone,and designed and used for that purpose. For example, the typicalapplication of a hip stem includes completely removing a femoral headand neck, implanting a hip stem, and using the hip stem to support anartificial femoral head.

In summary, and without limitation, the foregoing shows some of theshortcomings of the state of the art in this field. Among other things,what is needed is an orthopaedic implant system that includes a superiorsliding screw or other mechanism for applying compression across afracture. Some embodiments would also provide a sliding screw or othermechanism that obtains adequate bone purchase while reducing theincidence of cut-out, rotational instability, and excessive sliding. Ananatomically appropriately shaped implant for achieving improvedcortical bone contact would also be advantageous. Where the implant isan intramedullary nail, the nail would provide for reduced reaming andremoval of healthy bone. An improved nail may also have a cross-sectionthat provides a greater area of material on the side of the nail that isplaced under a greater tensile load when the nail is subjected to atypical bending load. Additionally, an improved implant system couldinclude a sliding screw in combination with intramedullary nails ofvarious designs, or in combination with plates. Combinations of any ofthese with each other or combinations of each other, and 1 or with otherdevices or combinations of them also present opportunities foradvancement beyond the state of the art according to certain aspects ofthe present invention.

SUMMARY OF THE INVENTION

Methods, devices and systems according to certain aspects of thisinvention allow treatment of bone fractures using one or both of astructure configured to be implanted in or stabilize a first bonefragment and a fastening assembly. The structure may take the form of aplate or other device for at least partial application to the outersurface of bone, or an implant for at least partial implantation withinbone. Such implants may include a proximal section having a transverseaperture, and an aperture substantially along their length. Preferably,they include at least one cross-section in their proximal portions whichfeatures a shape that imparts additional strength and resistance totension. Such shapes can be provided, for instance, by one or both (i)adding additional mass in lateral portions of the cross section, and (2)strategically adding and reducing mass in the cross section to takeadvantage of flange effects similar to the way flanges add structuralbenefits to I-beams and channels. One way to characterize suchcross-sections, which can but need not be asymmetrical with respect toat least one axis, is that they generally feature a moment of inertiaextending in a lateral direction from a point that is the midpoint of aline from a lateral tangent to a medial tangent of the cross section. Insome structures, that line is coplanar with the axis of the transverseaperture and coplanar with the cross section and thus defined by theintersection of those planes. The endpoints of that line can be definedas the intersection of the line with tangents to the medial aspect andthe lateral aspect of the cross section, respectively. Such implantsalso typically include a distal section and a transition section thatprovides a coupling between the proximal section and the distal section.

Fastening assemblies of methods, devices and systems according tocertain embodiments of the invention preferably include an engagingmember and a compression device. The fastening assemblies are adapted tobe received in the transverse aperture of the implant in a slidingrelationship, so that the fastening assembly is adapted to slide withrespect to the transverse aperture, and thus apply compression to afracture and for any other desired purpose. The engaging member isadapted to gain purchase in a second bone fragment. The engaging memberand the compression device are configured so that the compression deviceinteracts with a portion of the implant and also with a portion of theengaging member so that adjustment of the compression device controlssliding of the engaging member relative to the implant and therebyenables controlled movement between the first and second bone fragments.In some embodiments, the compression device at least partially directlycontacts the second bone fragment when implanted.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an intramedullary nail according to oneembodiment of the present invention shown installed in a femur.

FIG. 1A is a perspective view of an intramedullary nail according to oneembodiment of the present invention in greater detail.

FIG. 1B is a perspective view of an intramedullary nail according toanother embodiment of the present invention.

FIG. 1C is a cross-sectional view of a portion of the nail of FIG. 1B.

FIG. 1D is a perspective view of an intramedullary nail according toanother embodiment of the present invention.

FIG. 2 is an elevation view of the intramedullary nail of FIG. 1.

FIG. 3 is a cross-section view of the intramedullary nail of FIG. 2taken through the line 3-3.

FIG. 4 is a side view of the intramedullary nail of FIG. 2.

FIG. 5 is a cross-section view of the intramedullary nail of FIG. 4taken through the line 5-5.

FIG. 6 is a cross-section of the intramedullary nail of FIG. 4 takenthrough the line 6-6.

FIG. 7 is a perspective view of an intramedullary nail according to analternative embodiment of the invention.

FIG. 8 is a perspective view of an intramedullary nail according to analternative embodiment of the invention.

FIG. 9 is a perspective view of an intramedullary nail according to analternative embodiment of the invention.

FIG. 10 is a perspective view of an intramedullary nail according to analternative embodiment of the invention.

FIG. 11 is a perspective view of an intramedullary nail according to analternative embodiment of the invention.

FIG. 12 is a perspective view of an intramedullary nail according to analternative embodiment of the invention.

FIG. 13 is a cross-section view of the intramedullary nail of FIG. 7taken through line 13-13.

FIG. 14 is a cross-section view of the intramedullary nail of FIG. 8taken through line 14-14.

FIG. 15 is a cross-section view of the intramedullary nail of FIG. 9taken through line 15-15.

FIG. 16 is a cross-section view of the intramedullary nail of FIG. 10taken through line 16-16.

FIG. 17 is a cross-section view of the intramedullary nail of FIG. 11taken through line 17-17.

FIG. 18 is a cross-section view of the intramedullary nail of FIG. 12taken through line 18-18.

FIG. 19 is a perspective view of a tool according to an embodiment ofthe present invention for preparing bone to receive certain devicesaccording to certain embodiments of the present invention.

FIG. 20 is a perspective view of a device which includes a version of afastener assembly according to one embodiment of the present invention.

FIG. 21 is an exploded view of the intramedullary device and fastenerassembly shown in FIG. 20.

FIG. 22 is a perspective view of the fastener assembly shown in FIG. 20.

FIG. 23 is an exploded view of the fastener assembly of FIG. 20.

FIG. 24 is an elevation view of the engaging member of the fastenerassembly of FIG. 23.

FIG. 25 is a side view of the engaging member of FIG. 24.

FIG. 26 is a cross-section view of the engaging member of FIG. 24 takenthrough line 26-26.

FIG. 27 is an end view of one end of the engaging member of FIG. 24.

FIG. 28 is an end view of the other end of the engaging member of FIG.24.

FIG. 29 is an elevation view of the compression device of the fastenerassembly of FIG. 22.

FIG. 30 is a cross-section view of the compression device of FIG. 29shown through line 30-30.

FIG. 31 is an end view of one end of the compression device of FIG. 29.

FIG. 32 is an end view of the other end of the compression device ofFIG. 29.

FIG. 33 is a cross-section view of an intramedullary nail and screwassembly according to another embodiment of the present invention.

FIG. 34 is a perspective view of a fastener assembly according toanother embodiment of the invention.

FIG. 35 is a perspective view of the lag screw of the fastener assemblyof FIG. 34.

FIG. 36 is a perspective view of a fastener assembly according toanother embodiment of the invention.

FIG. 37 is a perspective view of the lag screw of the fastener assemblyof FIG. 36.

FIG. 38 is a perspective view of a fastener assembly according toanother embodiment of the invention.

FIG. 39 is an exploded view of the fastener assembly of FIG. 38.

FIG. 40 is a perspective view of a fastener assembly according toanother embodiment of the invention.

FIG. 41 is an exploded view of the fastener assembly of FIG. 40.

FIG. 42 is a perspective view of a compression plate according to anembodiment of the present invention which includes a fastener assemblyaccording to an embodiment of the invention.

FIG. 43 is a perspective view of a periarticular plate according to anembodiment of the present invention which includes a fastener assemblyaccording to an embodiment of the invention.

FIG. 44 is a perspective view of a device according to an embodiment ofthe present invention used in the context of humeral repair in ashoulder joint.

DETAILED DESCRIPTION

Methods, devices and systems according to embodiments of this inventionseek to provide improved treatment of femur fractures. FIGS. 1-6illustrate various views of one embodiment of an intramedullary nail 100of the present invention. The intramedullary nail 100 has a longitudinalbore 130 throughout to aid in insertion in the bone. The intramedullarynail 100 has a proximal section 102, a transition section 104 and adistal section 106.

The proximal section 102 of the particular structure shown in FIGS. 1-6preferably features an anatomically inspired shape that corresponds moreaccurately to typical cortical bone. One version of such shape is shownin the cross-sectional view of the proximal section 102 in FIG. 6. Theparticular cross-section of the proximal section 102 shown in FIG. 6 isgenerally non-circular along at least some portions of its length, andhas a lateral side or aspect 108 that is larger than a medial side oraspect 109. The lateral side 108 and medial side 109 are joined by afirst side 110 and a second side 116. At the intersection of the firstside 110 with the lateral side 108 is a first radiused corner 112 and atthe intersection of the second side 116 with the lateral side 108 is asecond radiused corner 114. The first side 110, second side 116 andlateral side 108 are of approximately equal length. The first side 110and second side 116 are oriented at acute angles relative to the lateralside 108, so that the medial side 109 is smaller than the lateral side108. By having the lateral side 108 larger than the medial side 109 therotational stability of the intramedullary nail 100 is increased, andresistance to bending and twisting can also be enhanced.

The medial side 109 shown in FIG. 6 can be radiused. As can be seen inFIG. 4, the radiused medial side 109 protrudes out from the transitionsection 104 and continues to the proximal end of the intramedullary nail100. The protrusion of the medial side 109 corresponds to the calcarregion of the femur and improves the evenness of load distributionbetween the bone and intramedullary nail 100.

Furthermore, the general cross-section geometry of the proximal sectionreduces peak stresses in the proximal section. More specifically, thetypical failure mode of an intramedullary nail and screw assemblycombination is failure of the nail in tension on its lateral side. Thetension is created by bending moment induced by body weight load that isapplied to the screw assembly. Therefore, it would be beneficial inreducing stress in the proximal section of a nail to include morematerial on the side of the nail that is in tension, the lateral side,to shape the cross section more effectively to enhance strength androbustness in the lateral area, or both. The design illustrated in FIG.6 accomplishes this objective. The lateral side 108 is wider than themedial side 109, thus imparting, at least partially, a flange-likeeffect. Stress per unit area induced in the material on the lateral side108 is less than would be the case if the lateral side was featured asmaller cross-sectional area, such as medial side 109.

A structure according to another embodiment of the invention thatbenefits from the same principle is shown in FIGS. 1B and 1C whichillustrate an intramedullary nail 1100 with a generally circular crosssection whose generally circular aperture 1128 is disposed other thanconcentric with the periphery of the cross section. In the particularstructure shown in these two Figures, the offset aperture 1128 is offsettoward the medial side 1109 such that a greater portion of material isavailable to take load, and reduce stress, on the lateral side 1108.Likewise, any cross-section that provides more material on the lateralside of the section reduces stress per unit area in the nail on thatside.

Regardless of the particular manner in which material or mass may beadded to some portions of the lateral parts of the cross section ofproximal portion 102, material may be added and removed from someportions of the cross section in order to increase the strength androbustness of the lateral parts, or both, the effect can becharacterized as imparting a moment of inertia to the cross sectionoriented at least partially in the direction of the lateral side oraspect 108. In a preferred embodiment, the moment of inertia (showndenoted by the letter M on FIG. 6) can be characterized as extending ina lateral direction, or at least partially toward lateral aspect or side108 from a point P that is the midpoint of a line L extending from theintersection I1 of that line with a tangent T1 to the lateral aspect108, to the intersection I2 of that line with a tangent T2 to the medialaspect 109. Stated another way, the effect in at least some cases is tocreate a cross section that features a moment of inertia extending in atleast partially lateral direction from a center of the cross section.Preferably, that center can be a midpoint between the lateral and medialedges of the cross section. Alternatively, that center can be the centerof mass of the cross section. The radius of gyration reflected by themoment of inertia, which is a function of the square of the distance ofthe incremental mass from the center, reflects additional strength inlateral parts of the proximal portion 102 caused by more mass or morestrategically placed mass in the cross section. In some structures, lineL is coplanar with the axis of the transverse aperture and coplanar withthe cross section and thus defined by the intersection of those planes.As FIGS. 1A, on the one hand, and 1B and 1C on the other hand reflect,and bearing in mind that these are only two of a myriad of structuresthat can impart such lateral additional strength and robustness, thecross section can but need not be asymmetrical with respect to at leastone of its axes. Additionally, the longitudinal opening 130 can belocated to share its central axis with that of the cross section, or itcan be offset in order to help impart the lateral strength or for otherpurposes.

In the particular device shown in FIGS. 1-6, the first side 110, secondside 116 and lateral side 108 are flat. Alternatively, these sides couldbe radiused or otherwise not flat. In the embodiment shown in FIGS. 1-6,the medial side 109 is radiused, but as one skilled in the art couldappreciate, the medial side could be flat.

The proximal section 102 has a transverse aperture 118 that receives afastening or screw assembly 200 (various versions of which are shown inFIGS. 19-41) through the intramedullary nail 100. One embodiment of theproximal transverse aperture 118, shown in FIGS. 1-4, is formed from twooverlapping circular apertures 120, 122, where the proximal circleaperture 120 is smaller in diameter than the distal circle aperture 122.The proximal circle aperture 120 shown has a shoulder 132 forconstraining the insertion depth of the screw assembly as will beexplained in more detail below. Various other apertures allowinginsertion of various screw assemblies could be used as would be known tothose skilled in the art. For example, FIG. 33 illustrates theintramedullary nail with a circular aperture. The embodiment of FIG. 33is described in greater detail below.

The proximal section 102 illustrated in FIG. 3 has a proximal endaperture 128. The proximal end aperture 128 is threaded to allow for theinsertion of a set screw that can be used to fix the rotational andsliding position of a screw assembly. A set screw may also includemechanisms for spanning a compression screw 204 (FIG. 19) andinterfering with a lag screw 202 (FIG. 19) to independently restrict therotation or sliding of the lag screw 202.

As shown in FIGS. 1-6, the transition section 104 is tapered from theproximal section 102 to the distal section 106. The tapered nature ofthe transition section 104 creates a press fit in the intramedullarycanal that controls subsidence. The tapered transition section 104assists in preventing the nail 100 from being pressed further down intothe intramedullary canal of the femur than intended.

In the embodiment of the intramedullary nail 100 shown in FIGS. 1-6, thecross-section of the transition section 104 is circular, but thecross-section could vary as known to those skilled in the art. Thecross-section could be anatomically derived, similar to thecross-section of the proximal section 102, oval or non-circular. In theembodiment shown in FIGS. 1-6, the transition section 104 contains adistal transverse aperture 124. The distal aperture 124 allows theinsertion through the intramedullary nail 100 of a distal locking screwfor locking of the intramedullary nail 100.

The distal section 106 of the intramedullary nail 100 is generallycylindrical and is configured to provide a reduced bending stiffness.The embodiment shown in FIGS. 1-5 has a longitudinal slot 126 throughthe center of the distal section 106 that forms two sides 134, 136. Theslot reduces bending stiffness at the distal end of the intramedullarynail 100 and reduces the chances of periprosthetic fractures.

FIG. 1D shows an intramedullary nail 100 according to another embodimentof the invention. This nail features, in its proximal portions, anoncircular cross section that is symmetrical with respect to itslateral-medial axis (in this case, preferably but not necessarily, ovalshaped in cross-section), and which features a centered longitudinalbore (in this case, preferably but not necessarily, circular incross-section). This nail achieves additional stability to the extent itresists twisting in the medullary canal. It also accomplishes the aim ofplacing more mass toward the lateral edge or aspect of the proximalcross section. Furthermore, it places additional mass toward the medialedge or aspect, and thus provides additional structure that acts as afulcrum to decrease the mechanical advantage of the fastening assemblywhich when loaded is the component that imposes tensional stress on thelateral edge or aspect.

FIGS. 7-18 illustrate intramedullary nails 100 according to otherembodiments of the invention. FIGS. 7 and 13 illustrate anintramedullary nail 100 having no longitudinal bore throughout.

FIGS. 8 and 14 illustrate an intramedullary nail 100 having stiffnessreduction slots 140 in the transition section 104 and the distal section106. The stiffness reduction slots 140 reduce the bending stiffness atthe distal end of the intramedullary nail 100 and could be used toreceive locking screws in some embodiments.

FIGS. 9 and 15 illustrate an intramedullary nail 100 having threelongitudinal slots 138 in the distal section 106 and a portion of thetransition section 104 forming a cloverleaf pattern. This pattern morereadily permits blood flow near the intramedullary nail 100 and alsoreduces bending stiffness at the distal end of the nail 100.

FIGS. 10 and 16 illustrate an intramedullary nail 100 in which thedistal section 106 and a portion of the transition section 104 have aseries of longitudinal grooves 146. The longitudinal grooves 146 reducebending stiffness at the distal end, provide rotational resistance, andenhance blood flow near the intramedullary nail 100.

FIGS. 11 and 17 illustrate an intramedullary nail 100 where thetransition section 104 and the distal section 106 have fins 144. Thefins 144 provide rotational resistance for the intramedullary nail 100.

FIGS. 12 and 18 illustrate an intramedullary nail 100 having barbs 142located on the distal section 106 and a portion of the transitionsection 104. The barbs 142 provide rotational resistance for theintramedullary nail 100.

Intramedullary nails according to the present invention may be insertedinto a patient by any suitable known technique. Generally, theintramedullary canal of the bone is prepared with an appropriate tool tocreate a void for insertion of the nail. Some portions of the void maybe prepared to be about 1 millimeter larger than the perimeter of thenail to permit sufficient space for blood flow after insertion of thenail. A guide pin or wire is optionally inserted into the preparedmedullary canal. The nail is then introduced into the desired position.If the nail is cannulated, the nail can be introduced over the guidewire. The position of the nail may be confirmed by imageintensification.

FIG. 19 shows one embodiment of a tool 300 for preparing a medullarycanal. The tool has a drill bit 302 for reaming and also a mortisechisel 304. In operation, the drill bit 302 reams out the medullarycanal of the femur and the mortise chisel 304 cuts out a larger sectionin the more proximal end of a bone. As shown in FIG. 19, the mortisechisel 304 has an anatomically derived cross-section of approximatelythe same shape as the proximal section of the intramedullary nail. Byapplying this type of shaped, mortise chisel, the proximal end of thenail will be better enabled to seat on cortical bone that has been onlyminimally altered. The mortise chisel 304 may be of a wide variety ofshapes, even complicated, asymmetrical shapes. This is advantageousbecause it enables a device and method for preparing voids able toaccept a wide variety of shapes of intramedullary nails without merelyover-reaming circular voids. Preparation of an accurately conformingvoid is valuable in avoiding unnecessary removal of healthy bone, and inensuring stable seating of the nail.

In operation, the tool 300 of the embodiment shown is advanced as aunit, with the drill bit 302 reaming and the mortise chisel 304 cuttingsimultaneously. The drill bit 302 may be turned with a power driver, orby hand. Likewise, the entire tool 300 may be advanced into a medullarycanal manually, or advanced with the assistance of mechanical advantageor power equipment. In other configurations, the drill bit 302 may becannulated (not shown) such that the entire tool 300 is operable overand guided by a guide wire that has been inserted into the medullarycanal.

In other embodiments, the bit for reaming is a more traditional reamerthat is separate from a cutting tool such as the mortise chisel 304. Themethod for preparing a void in such an instance would include firstreaming an opening with a traditional reamer. A device such as a chiselor a broach, shaped similar to the intramedullary nail to be implanted,would then be used to prepare the void. The chisel or broach may bedriven in by hand, with the assistance of a hammer or mallet, or withthe use of other power equipment. A nail consistent with the voidprepared would then be implanted.

Other custom instruments such as a contoured broach or a custom routerbit and template could be used as well. Broaches have long been used toprepare openings for hip stems, and the use of a broach would befamiliar to one of skill in the art. A router bit and template could beuse, in effect, to mill out the desired shape in the bone. Such a methodmight also be used in combination with reaming or broaching to createthe desired void.

The intramedullary nail of the present invention can be used to treatproximal femoral fractures and femoral shaft fractures, among otherfractures of long bones. When used to treat femoral shaft fractures, theintramedullary nail is secured in the femur by one or more fasteningdevices. When used for the treatment of proximal femoral fractures theintramedullary nail is preferably used in conjunction with a proximalscrew assembly.

FIGS. 20 and 21 illustrate an intramedullary nail 100 according to oneembodiment of the present invention used in conjunction with a fastenerassembly 200 according to one embodiment of the present invention. Thistype of fastener assembly may be used in various other bones and totreat a number of other indications, but for the purpose of providing anexample, it is being described here in use with the proximal femur. Ingeneral, the screw assembly is useful in any situation where onefragment of a bone is to be drawn back toward or pushed away fromanother fragment of the bone in a controlled manner. The fastenerassembly provides the additional advantage of being configurable toallow sliding of the assembly in a desired direction after the movementof the bone fragments has been accomplished.

As shown in FIG. 21, the axis of the proximal transverse aperture 118 inthe intramedullary nail 100 is angled relative to the proximal section102 and in use, is directed towards the femoral head. In this embodimentof the fastener assembly 200, an engaging member such as a lag screw 202is used in conjunction with a compression device, such as a compressionscrew 204 or a compression peg. The screws are configured such that whenin use the circumference of the lag screw 202 partially intersects withthe circumference of the compression screw 204, so that the compressionscrew 204 nests partially within the circumference of the lag screw 202.This particular combination of lag screw 202 and compression screw 204are further illustrated in FIGS. 22 through 32. Briefly, the lag screw202 shown in these figures is intended to engage the femoral head and toslide in the transverse aperture 118 of the nail 100. The compressionscrew 204 engages a shoulder or other structure in nail 100's transverseaperture 118 and also threads in the portion of lag screw 202 withinwhich compression screw 204 nests, so that rotation of compression screw204 controls sliding of the lag screw 202 relative to the nail 100 andthus compression of the femoral head against the fracture site.

The lag screw 202 shown in these drawings includes an elongate body 206and threaded end 208. As shown in FIGS. 24 and 25, the threaded end 208does not include a sharp end, which reduces the possibility of the cutout through the femoral head. The elongate body 206 includes a channel212 that allows for the positioning of the compression screw 204partially inside the circumference of the lag screw 202. The channel 212includes a threaded portion 210 that compliments and cooperates with athreaded section 214 of the compression screw 204. The compression screw204 includes a threaded section 214 and a head section 215. The threadedsection 214 of the compression screw 204 is configured such that thethreads are relatively flat and smooth at the exterior surface so thatthey can easily slide in the aperture and also reduce the possibility ofcut out.

The lag screw 202 is received in the proximal transverse aperture 118and into a pre-drilled hole in the femur so that the lag screw 202extends across the break and into the femoral head. The threaded end 208of the lag screw 202 engages the femoral head as the lag screw 202 isrotated within aperture 118 causing its threaded end 208 to engage thefemoral head. The threaded end 208 may be any device for obtainingpurchase in the femoral head, and includes but is not limited to,threads of any desired configuration including helices, barbs, blades,hooks, expanding devices, and the like. The placement depth of the lagscrew 202 into the femoral head differs depending on the desiredcompression of the fracture.

The compression screw 204 can also be received through the proximaltransverse aperture 118 into a predrilled hole in the femoral head. Thethreaded section 214 of the compression screw 204 engages with thethreaded portion of the channel 212 of the lag screw 202. The proximaltransverse aperture 118 has an interior shoulder 132 (FIG. 21) to limitthe sliding of the compression screw 204 in the general medial directionand, therefore, the lag screw 202, through the aperture 118. When thecompression screw 204 is tightened, the compression screw threads 214engage with the lag screw channel threaded portion 210 and thecompression screw 204 moves in the generally medial direction down thelag screw 202. The head section 215 of the compression screw 204 engagesthe shoulder 132 of the proximal transverse aperture 118 preventing thecompression screw 204 from moving further in the general medialdirection. As the compression screw 204 is tightened, the lag screw 202is drawn in the general lateral direction toward the intramedullary nailproviding compression to the fracture. The compression screw 204partially intersecting the circumference of the lag screw 202 providesgreater surface resistance and aids in the prevention of femoral headrotation. The compression screw 204 therefore acts not only as a part ofthe mechanism for moving fragments of the fractured bone relative to oneanother, but also directly contacts bone of the femoral head to helpprevent the femoral head from rotating about the axis of the lag screw202.

In one embodiment, a set screw (not shown), positioned in the proximalend aperture 128 of the intramedullary nail, is used to engage thecompression screw 204 and fix the compression screw 204 and lag screw202 in place. The use of the set screw to fix the fastener assembly 200in place is fracture pattern dependent. If a set screw is not used toengage the fastener assembly, the fastener assembly 200 can slide withinthe proximal aperture limited by the shoulder 132.

In the embodiment of the lag screw and compression screw shown in FIGS.20-32, the diameter of the compression screw 204 is smaller than thediameter of the lag screw 202. The diameters of the lag screw andcompression screw could be the same or the diameter of the lag screwcould be smaller than the diameter of the compression screw. The threadsof the lag screw and the compression screw could be a variety ofdifferent shapes as known to those skilled in the art. In general, thepurpose of the lag screw is to obtain purchase in bone, and the purposeof the compression screw is to engage with and draw or move the lagscrew. Any configuration that permits these functions is within thescope of the invention.

The fastener assembly could additionally be configured to allow theaddition of a prosthetic femoral head and neck. In such an embodiment,the lag screw 202 would be replaced with a prosthetic head and neck. Theneck would fit into the proximal transverse aperture 118 in the nail100. The design would be beneficial where degeneration or re-injury of arepaired femoral fracture and hip joint later necessitated a total hiparthroplasty (THA). The decision to accomplish a THA could be madeinteroperatively, or after some period of time. Instead of having toprepare a femur to accept a hip stem as is known in association withTHA, only a small portion of bone would need to be removed, along withthe fastener assembly 200. The prosthetic head and neck could then beinserted into the proximal transverse aperture 118, the acetabulumprepared, and the remainder of the THA completed.

FIG. 33 is a cross-section view of an intramedullary nail 100 accordingto another embodiment of the invention with an alternate fastenerassembly 400. The fastener assembly illustrated is very similar to thecompressing fastener assembly of Smith & Nephew's IMHS@ system, as ismore thoroughly disclosed in U.S. Pat. No. 5,032,125, which is herebyincorporated by reference, and various related international patents.The improvement of the device illustrated is that it includes theintramedullary nail 100 with an anatomically derived shape and itsmultiple advantages as discussed above. In operation, a sleeve 401 fitsthrough the intramedullary nail 100, and may be secured to the nail byset screw, or other effective mechanisms. A sliding lag screw 402 isable to move axially within the sleeve 401. A compressing screw 404 isthreaded into the sliding lag screw 402 such that tightening of thecompressing screw 404 draws the sliding lag screw 402 back into thesleeve 401. With this mechanism, a bone fragment may be brought into adesired position, but still permitted to achieve sliding compressiononce positioned.

FIGS. 34-35 illustrate a fastener assembly 200 according to anotherembodiment of the invention having a lag screw 202 and a compression peg502. As shown in FIG. 34, the lag screw 202 and the compression peg 502are configured such that, when in use, the circumference of the lagscrew 202 partially intersects with the circumference of the compressionpeg 502, although in some embodiments the circumferences might beadjacent rather than intersecting. The lag screw 202 includes anelongate body 206 and threaded end 208. The lag screw 202 has a key 504on the channel 212. The compression peg 502 has a slot 503 that isadapted to receive the key 504 of the lag screw 202. The key 504 andslot 503 can be a variety of complimentary shapes, such as, whenconsidered in cross section, triangular, D-shaped, key-holed and othershapes as are apparent to those skilled in the art. In operation, thecompression peg 502 may be moved relative to the lag screw 202 by acompression tool (not shown) that applies disparate forces between thecompression peg 502 and the lag screw 202, or between the entireassembly and the intramedullary nail 100.

In the fastener assembly 200 shown in FIGS. 34-35, the lag screw 202 isreceived to slide in a proximal aperture of the intramedullary nail sothat the lag screw 202 extends across the break and into the femoralhead. The threaded end 208 of the lag screw 202 engages the femoralhead. Once the lag screw 200 has been properly engaged with the femoralhead, the compression peg 502 is inserted in the proximal aperture intoa predrilled hole in the femoral head, in order to prevent furtherrotation of the lag screw 202 as the slot 503 of the compression peg 502receives the key 504 of the lag screw 202. By providing more area forresistance, the compression peg 502 helps to prevent the rotation of thefemoral head on the lag screw 202. The compression peg 502 is fixed inposition in the intramedullary nail 100 by a set screw positioned in theproximal end aperture of the nail. The lag screw 202 can slide on thecompression peg 502 through the proximal aperture. In anotherembodiment, the compression peg 502 has barbs on its surface.

A fastener assembly 200 according to another embodiment of the inventionis illustrated in FIGS. 36-37. The fastener assembly 200 of thisembodiment has a compression peg 502 and a lag screw 202 similar to theembodiment illustrated in FIGS. 34-35 except that the key 504 of the lagscrew 202 and the slot 503 of the compression peg 502 have complimentaryratchet teeth 506. The compression peg 502 is fixed in position in theintramedullary nail by a set screw positioned in the proximal endaperture. Compression of the fracture can be achieved by pulling the lagscrew in the general lateral direction. The ratchet teeth 506 allow thelag screw 202 to move in the general lateral direction, but prevent thelag screw 202 from moving in the general medial direction. A compressiontool similar to the tool describe in association with FIGS. 34-35 may beused to accomplish the movement.

FIGS. 38-39 a fastener assembly 200 according to another embodiment ofthe invention having a lag screw 602, a cross hair screw 610 and acompression screw 604. The lag screw 602 includes an elongate body 606and threaded end 608. The elongate body 606 is semi-circular shaped incross section. The screws 602, 604, 610 are configured so that thecircumference of the lag screw 602 intersects with the circumferences ofthe cross hair screw 610 and the compression screw 604. The elongatebody 606 of the lag screw 602 is threaded to compliment and cooperatewith a threaded section 602 of the cross hair screw 610. The cross hairscrew 610 is threaded to engage with the lag screw 602 and thecompression screw 604. The compression screw 604 includes a threadedportion 614 and a head portion 612.

In this embodiment, the lag screw 602, the cross hair screw 610 and thecompression screw 604 are received simultaneously to slide in a proximalaperture of an intramedullary screw. The lag screw 602 extends acrossthe break and into the femoral head. The threaded end 608 of the lagscrew 602 engages the femoral head. As compression screw 604 istightened, the threads 614 of the compression screw engage the threadsof the cross hair screw 610 and lag screw 602, thereby moving the lagscrew 602 in the general lateral direction toward the intramedullarynail providing compression to the femoral head. The cross hair screw 610is then turned causing the compression screw 604 to move in the distaldirection away from the lag screw 602. The fastener assembly 200 canalternatively be configured so that the compression screw 604 movesproximally relative to the lag screw 602. The compression screw 604separate from the lag screw 602 helps to prevent rotation of the femoralhead on the lag screw 602 by adding more area for resistance.

FIGS. 40-41 illustrate a fastener assembly 200 according to anotherembodiment of the invention having a lag screw 702 and a compression peg704. The lag screw 702 includes an elongate body 706 and a threaded end708. The elongate body 706 is semi-circular shaped in order to allow thecompression peg 704 to be positioned partially inside the circumferenceof the lag screw 702 for insertion into the femur and has a key 712positioned on the interior side of the elongate body 706. The elongatebody 706 also has an aperture 710 through the body. The compression peg704 is generally cylindrical and is sized to fit within thesemi-circular body 706 of the lag screw. The key 712 of the lag screw isreceived by a slot 714 in the compression peg 704. The key 712 and slot714 contain complimentary ratchet teeth.

In this embodiment, the lag screw 702 and the compression peg 704 arereceived simultaneously to slide in a proximal aperture of anintramedullary screw into a pre-drilled hole in the femur. The lag screw702 extends across the break and into the femoral head. The threaded endof the lag screw 702 engages the femoral head. A compression toolsimilar to the tool describe in association with FIGS. 34-35 may be usedto accomplish movement between the compression peg 704 and the lag screw702, or between the entire assembly and the intramedullary nail 100. Aset screw may used to fix the position of the fastener assembly. The setscrew is configured such that when the set screw is tightened aprotrusion on the set screw is received through the slot 710 of the lagscrew 702 and moves the compression screw 704 away from the lag screw702. The compression screw 704 separate from the lag screw 702 helps toprevent rotation of the femoral head on the lag screw by adding morearea for resistance.

FIG. 42 illustrates another embodiment of the invention where a fastenerassembly 200 is employed in cooperation with a compression plate 150. Asillustrated, the devices are being applied to a femur. The variousembodiments of the fastener assembly 200 disclosed above may be usedwith a similar compression plate, and various compression plates may beconfigured to be applicable to other parts of the anatomy.

FIG. 43 illustrates another embodiment of the invention where a fastenerassembly 200 is being used with a periarticular plate 170. The plate andfastener assembly shown are being applied to a proximal tibia. Thevarious embodiments of the fastener assembly 200 disclosed above may beused with a similar periarticular plate and various periarticular platesmay be configured to be applicable to other parts of the anatomy.

FIG. 44 illustrates another embodiment of the invention where a fastenerassembly 200 is used in combination with a humeral nail 190. Asillustrated, a head section 212 of compression screw 204 bears againstthe humerus to draw compression against the humerus. With thecompression force applied to lag screw 202, and the lag screw 202affixed to a bone fragment through its threaded end 208, the bonefragment may be drawn into position for proper healing. In somecircumstances, it may be advantageous to place a washer or bearingsurface (not shown) between the head section 212 and the humeral boneagainst which the head section 212 compresses. In yet another variant,the opening in the humerus may be enlarged such that head section 212 ispermitted to penetrate the humerus and bear against a portion of thehumeral nail 190. In such an embodiment, the fastener assembly 200 wouldbe shorter than illustrated in FIG. 44 to obtain purchase in the samearea of bone with the threaded end 208. The various embodiments of thefastener assembly 200 disclosed above may be used with a similar nailand various nails may be configured to be applicable to other parts ofthe anatomy.

As those skilled in the art will appreciate, the particular embodimentsof this invention described above and illustrated in the figures areprovided for explaining the invention and various alterations may bemade in the structure and materials of the illustrated embodimentswithout departing from the spirit and scope of the invention asdescribed above and in the following claims.

What is claimed is:
 1. An intramedullary nail, comprising: alongitudinally extending member having a proximal region, a distalregion, and a central longitudinal axis; the member defining alongitudinal bore and a transverse aperture; and the longitudinal borebeing offset from the central longitudinal axis at least in a portion ofthe proximal region spaced from the transverse aperture, the portion ofthe proximal region including a non-circular cross-section at least aportion of the proximal region having a non-circular cross-sectionperpendicular to the central longitudinal axis of the member, thenon-circular cross section excluding the transverse aperture andincluding the longitudinal bore, the longitudinal bore included in thecross-section having a center that is offset from the centrallongitudinal axis of the member.
 2. The intramedullary nail of claim 1,wherein a lateral side of the member included in the non-circularcross-section is larger than a medial side of the member included in thenon-circular cross-section.
 3. The intramedullary nail of claim 1,wherein the member includes a medial side having radiused corners. 4.The intramedullary nail of claim 3, wherein the member includes alateral side having radiused corners.
 5. The intramedullary nail ofclaim 1, wherein the member includes a lateral side and a medial sidethat are joined by a first side and a second side.
 6. The intramedullarynail of claim 5, wherein the first and second sides are not parallel andare oriented at acute angles relative to the lateral side.
 7. Theintramedullary nail of claim 5, wherein the first and second sides andthe lateral side included in the cross-section are approximately thesame size.
 8. The intramedullary nail of claim 1, wherein the memberincludes a medial side that is generally semi-circular.
 9. Theintramedullary nail of claim 1, wherein a center of the longitudinalbore is offset from the central longitudinal axis of the member towardsa medial side.
 10. The intramedullary nail of claim 1, wherein at leasta portion of the distal region includes a circular cross-section. 11.The intramedullary nail of claim 1, wherein a center of mass of theportion of the proximal region having the non-circular cross-sectionincludes a center of mass that is offset from a geometric center of theportion of the proximal region towards a lateral side.